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So recently I took my car to get an alignment done and we discovered that my coolant was leaking out (had a small puddle under it in the shop). Turns out they let the car idle for the whole time they are doing the alignment, and it appears that the expansion tank basically starts to expand/fill up and then flow out the top. So I started wondering why is this happening?
I took it home to duplicate, and sure enough, while letting it idle in my garage the expansion tank starts to raise and would likely overflow if I left it to run long enough.
HOWEVER....
What I DID notice while doing this is that the radiator fan (standard fan, not the A/C Condensor fan) never turned on. It briefly, and I mean like .5 seconds, started to spin up and then immediately shut off. It never really turned on and stayed on for even a little bit. BUT, if I turn on the A/C, both fans immediately kick in and run until they no longer need to, then they shut off. Kick back in again....run....then shut off. So the only time I can get either of my fans to run is to run the A/C all of the time. And yes I am heating the car up to 3 bars, and then letting it idle for like 15-20 minutes.
SOOO...In an effort to try and troubleshoot I did check and the heater does put out heat, so from what I can tell the thermostat isn't the issue (unless there is something I am missing).
I also tried swapping the relays for both of the fans since they are the same part. I heated the car back up to temp, tested and both turn on when running the A/C, but the regular cooling fan never turned on at all, no matter how long I let it run.
So it's pretty apparent that since the regular cooling fan never turns on (I didn't notice until winter, since I am in Florida and we almost ALWAYS run the A/C down here) when I drive without a/c, it heats up coolant so much in the expansion tank that it overflows. (Also, the puddle we saw was right under where the expansion tank would be, plus it's brand new and I can see where coolant has leaked down it).
So any ideas why my regular cooling fan will not turn on unless the A/C is on? I'm searching online and not having much luck finding anything that addresses this particularly.
Any ideas/help are welcomed! Thanks in advance folks!!
Cool, thanks Chuck! Yeah, that is actually the next thing on my list to TS. I am having a hell of a time getting it disconnected from up above, so will probably have to try jacking it up and trying to access it from underneath. That's the plan for tomorrow. And thanks for the heads up on the service manual. I'll check that section and see what it says. I'll update once I get that tested. I plan to try closing the circuit with paper clip and see if she turns on. I'll update with results when I have them.
Looks like a round connector to the switch which screws into the radiator bottom. Part number 37760-P00-003. It may be a generic Honda part but fits the 00-05 S2000.
Cool, thanks. Yeah that's what I what I came up with, too. Biggest headache was not destroying those push pins when I removed the under panel to get to it.
Although I want to make sure I understand this correctly and that everything is running right. If you refer to my attached image, I disconnected the plug for the Radiator Fan Switch (circled), bridged that plug connecter with a paper clip, and the both fans came on. Is that what is supposed to happen? Both of the them turn on? I presume this means the switch is bad, that it's not triggering them to come on when the coolant gets hot, right? But what I am confused about are the fans. Are they always supposed to come on together? I thought only one fan was supposed to come on when the A/C wasn't running (the passenger side fan), and both only come on when the A/C is turned on.
Also, I presume it's fine to buy an aftermarket switch, and not OEM, right? Do they usually hold up?
Wild guess. Check your radiator cap. I think your cap isn't holding pressure. You can easily test this, start the car, the upper hose should feel firm with the engine running. If you can easily squeeze the hose, your cap isn't holding pressure. If your rad isn't holding pressure water will boil off the overflow. Remember raising pressure raises the boiling point of water.
When your cap doesn't hold pressure, coolant cannot be pumped through the system as efficiently. So it takes longer to get to and from the radiator.
This manifests as cooling fans cycling on for very low periods.
I checked that when I was TS'ing it earlier and letting it idle for 20 minutes to see if the fans ever turned on. Plus I replaced the radiator and cap about 5 years ago so they aren't that old. Top hose was firm.
Page 10-19 of the service manual notes that if the fan(s) run when the terminals on the switch are jumpered but not at high engine heat the fan switch is bad. Replace the fan switch. (You did download the Service Manual, right?) You can roll the dice on an aftermarket switch -- Honda didn't make it anyway. I suspect these are generic to several Honda/Acura cars.
My '06 runs both fans when engine temp is high enough. I "thought" only 1 fan ran unless the AC was on but this is not the case with my '06 (which does not have the switch of the earlier cars and runs the fans off the ECU).
Cool, thanks Chuck. Yeah I do have the manual (the European one on ISO, unless you have a different one) but when I launched my Win XP VM to run the manual software, it Blue Screened for some reason and I haven't had a chance to TS that yet, either. LOL! When it rains it pours, huh.
OK, well I'll definitely put the fan switch down as the culprit. It's nice to know you get the same fan behavior as well, even though yours isn't the same configuration.
Thanks again for your help! It's is greatly appreciated!
01-23-2021, 01:34 PM
Radiator fan only turns on when A/C is turned on.
